1. Field of the Invention
The present invention generally relates to image transformation methods and apparatuses, image recognition apparatuses, robot control apparatus and image projection apparatuses, and more particularly to image transformation method and apparatus for obtaining position coordinates by transforming image information picked up (or imaged) by an image pickup device (or imaging device), an image recognition apparatus for recognizing an image based on the position coordinates obtained by such an image transformation method, a robot control apparatus which uses such an image recognition apparatus, and an image projection apparatus which uses such an image transformation method.
2. Description of the Related Art
When assembling parts, devices and the like using a robot, it is necessary to accurately control movements of each part of an arm, a hand and the like of the robot. For example, when mounting a part on a substrate, the position of the robot hand with respect to the substrate can be detected based on an image which is picked up by a camera that is provided on the robot hand. However, as the movements of the robot hand become complex, the camera cannot always pickup the image in a direction perpendicular to the substrate surface. The robot hand may be moved to a position above the substrate surface from an outer side the substrate in a direction tilted with respect to the substrate surface, for example. In such a case, it is difficult to accurately detect various shapes within the image and the position of the robot hand above the substrate surface, based on the image which is picked up from the direction tilted with respect to the substrate surface. This is because an angle formed by an optical axis of the camera and the substrate surface is not always constant.
It is possible to provide marks on the substrate surface and use the marks as references within the picked up image, so as to improve to a certain extent the shape detection accuracy with which the various shapes within the image are detected and the position detection accuracy with which the position of the robot hand. However, in order to improve the shape detection accuracy with respect to the various shapes within the image and the position detection accuracy with respect to the robot hand, it is necessary to increase the number of marks. But depending on the number and size of the parts to be mounted on the substrate, there is a limit to the number of marks that may be provided on the substrate, and further, the marks may become hidden by the mounted parts.
If the shape detection accuracy with respect to the various shapes within the picked up image is poor, the image recognition accuracy using the picked up image deteriorates. In addition, when the shape detection accuracy with respect to the various shapes within the picked up image and the position detection accuracy with respect to the robot hand are poor, the mounting position accuracy of the parts mounted on the substrate deteriorates, and the robot hand may hit the substrate or the parts on the substrate when the robot hand is moved. For this reason, there are demands to improve the shape detection accuracy with respect to the various shapes within the picked up image and the position detection accuracy with respect to the robot hand, that is, to accurately detect the position coordinates within the picked up image.
On the other hand, in the image projection apparatuses such as a projector, an image is projected onto a screen or the like. But it is difficult to set up the image projection apparatus so that an optical axis of the image projection apparatus is perpendicular to the screen, and it may be impossible in some cases due to space restrictions. When the optical axis of the image projection apparatus is tilted with respect to the screen, the image projected onto the screen becomes distorted, and for example, an originally rectangular shape may be distorted and projected as a trapezoidal shape on the screen. The distortion of the image projected on the screen not only deteriorates the picture quality, but also makes the image awkward, unnatural and sometimes unpleasant to the viewer.
Conventionally, a system has been proposed to correct a vertical (up-and-down direction) distortion in the image projected on the screen by the so-called trapezoidal correction to correct the trapezoidal shape generated by the distortion into the rectangular shape. In addition, another system has been proposed to correct a horizontal (right-and-left direction) distortion in the image projected on the screen by the so-called trapezoidal correction to correct the trapezoidal shape generated by the distortion into the rectangular shape. The after system is employed in a side-shot projector, such as the projector VPL-HS1 (product name CINEZA) manufactured by SONY CORPORATION OF JAPAN, for example.
However, the conventional systems which use the trapezoidal correction cannot cope with a case where the optical axis of the image projection apparatus is tilted by an arbitrary angle in both the vertical direction and in the horizontal direction with respect to the screen. That is, the conventional system cannot cope with the case where the projection is at an arbitrary angle with respect to the screen. For this reason, there is a limit to improving the picture quality on the screen.